BMS 108 Ch. 20 Reproductive System Flashcards
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How many chromosomes does each gamete have? What is a cell with 46 chromosomes called? 23?
23; diploid; haploid
What is a gamete?
a sex cell formed in the gonads by meiosis
What is a zygote?
a 46 chromosome cell resulting from fusion of sperm and egg during fertilization
Each zygote inherits 23 chromosomes from mother and 23 from father. Producing 23 pairs of ___________ chromosomes. 22 of these are ___________ chromosomes and the 23rd pair are __________ chromosomes.
homologous; autosomal; sex
What are the sex chromosomes of a female? male?
XX; XY
How is chromosomal gender of the zygote determined?
All ova contain X chromosomes, some sperm contain X chromosomes and others contain Y chromosomes. Which type of sperm fertilizes the egg determines the sex of the zygote.
What chromosome induces the formation of testes?
Y chromosome
What induces the formation of male sex organs?
testosterone from the testes
Gametes are produced by what process?
Meiosis
There are two phases of meiosis, meiosis I and meiosis II. Where does the reduction in genetic material occur?
meiosis I
What are the four phases of meiosis I? Meiosis II?
Prophase, metaphase, anaphase, telephase; same as meiosis I
Describe the general interactions between the hypothalamus, anterior pituitary and gonads in the production of gametes.
- Hypothalamus releases GnRH to anterior pituitary
- Anterior pituitary releases LH and FSH which stimulates the production of sperm and eggs and gonadal sex steroids; also maintains the size of gonads
- sex steroids provide negative feedback to the hypothalamus and anterior pituitary
- gonads also secrete the hormone inhibin, which negatively feeds back on FSH secretion
What causes puberty?
- FSH and LH secretion is high for first 6 mos. of life, but fall to very low levels until puberty
- At puberty hypothalamus increases GnRH secretion»_space;> increases FSH and LH secretion
- Stimulates sex steroid secretion»_space;> drives changes in secondary sex characteristics and menarche (first menstrual flow)
What determines age of puberty in girls?
% body fat and activity level. Girls with low body fat and high activity levels enter puberty at an older age
What is an ovarian follicle?
an oocyte + surrounding follicle cells
What do follicle cells secrete?
estrogen
Describe the production of oocytes.
- At 5 month gestation, ovaries contain 6-7 million oogonia
- Toward the end of gestation, oogonia become primary ooctyes and begin meiosis I, but arrest in prophase (2n)
- There is continual loss of primary oocytes throughout life (2 million left at birth, 400,000 left at puberty)
- 400 oocytes are ovulated during reproductive years, the rest undergo apoptosis (programmed cell death)
Describe the process of follicular development.
- Primary follicle contains a primary ooctye & a layer of follicle cells
- In response to FSH, some follicles enter the ovarian cycle and grow
- Some primary follicles continue to develop and become secondary follicles (same as primary follicle but has more follicle cells and antrum)
- Graafian (mature) follicle contains a secondary ooctye (n) and is ready for ovulation
What is the menstrual cycle?
a month long cycle of ovarian activity characterized by shedding of endometrial lining of the uterus and bleeding (menstruation)
What is the follicular phase?
- Lasts from day 1 to about 13
- Dominated by growth of primary follicles into secondary follicles & production of estradiol
- One survivor becomes a graafian follicle, reaching peak at about day 12
What is follicular growth and estrogen secretion dependent on?
FSH from the Anterior Pituitary
What kind of receptors does FSH and estrogen recruit in graafian follicles?
LH
Describe how the events in the follicular phase cause ovulation.
- Rapidly rising estrogen secretion causes the hypothalamus to increase pulses of GnRH, resulting in greater LH secretion
- A positive feedback between estrogen and anterior pituitary develops, resulting in a LH surge that causes ovulation
What is the phase that follows the follicular phase?
the luteal phase
Describe the luteal phase.
- After ovulation, LH causes the empty follicle to become the corpus luteum, secreting estrogen, progesterone & inhibin
- This exerts negative feedback on LH and FSH (inhibin inhibits FSH only)
- High estrogen and progesterone also triggers uterine lining buildup
- If no fertilization occurs, corpus luteum regresses, causing estrogen and progesterone levels to drop
- Causing menstruation and allowing a new cycle of follicle development
In addition to the hormonal phases, there are also 3 cocurrent endometrial phases during the mentrual cycle. What are the 3 endometrial phases?
- Menstrual
- Proliferation
- Secretory
The male reproductive system makes _____ and secretes ______.
sperm; androgens
Where is sperm made?
seminiferous tubules
What FSH receptive cells initial spermatogenesis?
Sertoli cells
What are the cells that secrete testosterone called? Where are they located?
Leydig cells; in the interstitial tissue in the seminiferous tubules
In the male reproductive system, what inhibits GnRH? LH? FSH?
Testosterone; Testosterone; Inhibin
Describe hormonal control of the male reproductive system.
- Hypothalamus secrets GnRH»_space;> Ant. Pit.»_space;> FSH & LH
- FSH stimulates Sertoli cells, starting spermatogenesis and secreting inhibin
- Inhibin causes negative feedback on FSH
- LH stimulates Leydig cells, causing testosterone to be released
- Testosterone inhibits LH in the Ant. Pit.
What are the Sertoli cells functions?
- Blood testes barrier
- Nurture developing spermatozoa
- Respond to FSH (ant. pit.) & Testosterone (Leydig) which stimulates spermiogenesis
- Secrete Inhibin (negative feedback on FSH production)
Describe the process of making sperm.
- Spermatogonia (stem cells) replicate via mitosis
- Spermatogonia that will continue to develop is a primary spermatocyte
- Primary spermatocyte undergoes meosis I and become a haploid secondary spermatocyte
- Secondary spermatocyte undergoes meiosis II to make spermatids
- Spermatids undergo spermiogenesis to become sperm
All this takes place in the seminiferous tubules and involves sertoli (nurse) cells
Why does spermatogenesis start with mitosis?
to keep our starter cells
What does a spermatid develop during spermiogenesis?
a flagellum and acrosome cap
What is an acrosome cap?
A cap of digestive enzymes for burrowing into an oocyte
What are the functions of the male accessory sex organs?
sperm motility, seminal fluid secretion, and ejaculation
Why aren’t spermatozoa motile when entering the epididymus?
due to low pH
What do the seminal vesicles add to the seminal fluid?
fructose (nutrients)
What does the prostate add to the seminal fluid?
neutralizes pH, adds citric acid (nutrients) and coagulation proteins
What do the bulbourethral gland add to the seminal fluid?
lubrication for the urethra and neutralizes pH
What part of the ANS controls erection? ejaculation?
parasympathetic; sympathetic
